Ultrasonography is one of image diagnostic methods capable of forming highly sensitive images of blood vessels by administration of a contrast medium into the blood vessels. In Japan, the use of a contrast medium called Sonazoid is currently approved for diagnosing liver tumors and mammary tumors. The contrast medium of Sonazoid is employed for deciding types of tumors.
In practical situations of diagnosis, an operator initially checks the presence or absence of a tumor. A tumor is recognized as a hypoechogenic region or a hyperechogenic region in an ultrasonic image. Then, a contrast medium is administrated, and the tumor is imaged.
At present, a tumor type decision is made based on subjective decision of a person reading images (operator). This situation causes a problem that diagnosis results are dependent on the person reading the images.
For overcoming this problem, Patent Literature 1 discloses objective differential diagnostic methods based on time-series changes of two types of feature values, i.e., average luminance and standard deviations exhibited in a tumor region.
According to the technology disclosed in Patent Literature 1, large and small three circles containing a tumor are defined, and comparisons are made between temporal waveforms of the feature values in the respective circles and typical waveforms of respective types. Then, the type producing the closest waveforms is decided as the type of the tumor. Alternatively, the type producing feature values closest to the feature values of the three circles is decided for each time phase. Then, the type decided the largest number of times is decided as the type of the tumor.